python - string总结

Strings

• Strings are immutable.
• Strings are sequences.
• Strings have many methods. See Table 4.2.
• Standard operations:
  • length function: len(s)
  • membership:in

Indexing and Slicing

Given: s = 'Mississippi'

• Indexing starts at 0: s[0] is 'M'.
• Negative indices work backward from the end: s[-1] is 'i'.
• Slicing selects a subset up to but not including the final index: s[3:6] is 'sis'.
• Slicing default start is the beginning, so s[:4] is 'Miss'.
• Slicing default end is the end, so s[7:] is 'ippi'.
• Using both defaults makes a copy: s[:].
• Slicing’s optional third argument indicates step: s[:6:2] is 'Msi'.
• The idiom to reverse a string: s[::-1] is 'ippississiM'

Formatting

{arg:[[fill]align][sign][#][0][minimum width][,][.precision]type}

Iteration: for, enumerate

• for walks through each character in a string:

for ch in 'Mississippi':

• enumerate generates both the index and the character:

for index, ch in enumerate('Mississippi'):